让滚动条滚动
window上有三个方法
scoll(),scollTo(),scollBy()累加滚动
<!DOCTYPE html>
<html>
<head>
	<title></title>

</head>
<body>
	<div></div>
	<div></div>
</body>
</html>

<script type="text/javascript">
	window.scoll(10,100)
	var start = document.getElementsByTagName('div')[0];
	var timer = 0;
	var key = true;//加锁
	start.onclick = function (){
		if(key){
			timer = setIntervel(function(){
			window.scollBy(0,10);
			},100)
		}
		key = false;
		
	}
	stop.onclick = function (){
		clearInterval(timer);
		key = true;
	}
</script>